This application is based on Application No. 2001-160392, filed in Japan on May 29, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an automotive alternator provided with a stator in which a stator winding is installed in a stator core having two slots per phase per pole, and particularly relates to a stator construction in which a stator winding constructed by connecting together winding phase portions having a phase difference corresponding to an electrical angle of 30 degrees is installed.
2. Description of the Related Art
FIG. 24 is a longitudinal section showing a first conventional automotive alternator, FIG. 25 is a perspective showing a first stator used in the first conventional automotive alternator, and FIG. 26 is a circuit diagram showing an electric circuit in the first conventional automotive alternator.
In FIGS. 24 and 25, a first conventional automotive alternator includes: a case 3 constituted by a front bracket 1 and a rear bracket 2 made of aluminum; a shaft 6 disposed inside the case 3, a pulley 4 being secured to a first end portion of the shaft 6; a Lundell-type rotor 7 secured to the shaft 6; fans 5 secured to first and second axial end portions of the rotor 7; a first stator 8 secured to the case 3 so as to envelop the rotor 7; slip rings 9 secured to a second end portion of the shaft 6 for supplying electric current to the rotor 7; a pair of brushes 10 sliding on surfaces of the slip rings 9; a brush holder 11 for housing the brushes 10; first and second rectifiers 12A and 12B electrically connected to the first stator 8 for converting alternating current generated in the first stator 8 into direct current; and a regulator 18 mounted to a heat sink 17 fitted onto the brush holder 11, the regulator 18 adjusting the magnitude of the alternating voltage generated in the first stator 8.
The rotor 7 includes: a field winding 13 for generating magnetic flux on passage of an electric current; and a pair of first and second pole cores 20 and 21 disposed so as to cover the field winding 13, magnetic poles being formed in the first and second pole cores 20 and 21 by magnetic flux from the field winding. The first and second pole cores 20 and 21 are made of iron, each has six first and second claw-shaped magnetic poles 22 and 23 each having a generally trapezoidal outermost diameter surface shape disposed on an outer circumferential edge portion at even angular pitch in a circumferential direction so as to project axially, and the first and second pole cores 20 and 21 are fixed to the shaft 6 facing each other such that the first and second claw-shaped magnetic poles 22 and 23 intermesh. In other words, the number of magnetic poles in this rotor 7 is twelve.
The first stator 8 is constituted by: a cylindrical stator core 15 composed of a laminated body of magnetic plates; and a first stator winding 16 installed in the stator core 15.
The first stator 8 is held between the front bracket 1 and the rear bracket 2 so as to form a uniform air gap between outer circumferential surfaces of the claw-shaped magnetic poles 22 and 23 and an inner circumferential surface of the stator core 15. Seventy-two slots 15a opening onto an inner circumferential side are formed in the stator core 15 at an even angular pitch in a circumferential direction. In other words, the slots 15a are formed at a ratio of two per phase per pole, adjacent pairs of the slots 15a having a phase difference corresponding to an electrical angle of 30 degrees.
The first stator winding 16 is constituted by an a-phase winding phase portion 30a, a b-phase winding phase portion 30b, a c-phase winding phase portion 30c, a d-phase winding phase portion 30d, an e-phase winding phase portion 30e, and an f-phase winding phase portion 30f in each of which a continuous wire is installed in a wave shape in every sixth slot 15a. The a-phase winding phase portion 30a, the b-phase winding phase portion 30b, and the c-phase winding phase portion 30c are formed into a Y connection, constituting a first three-phase alternating current winding 160A, and the d-phase winding phase portion 30d, the e-phase winding phase portion 30e, and the f-phase winding phase portion 30f are formed into a Y connection, constituting a second three-phase alternating current winding 160B. The first and second three-phase alternating current windings 160A and 160B are connected to the first and second rectifiers 12A and 12B, respectively, constituting the electric circuit shown in FIG. 26.
A specific construction of the first stator winding 16 will now be explained with reference to FIGS. 27A to 28.
First, as shown in FIG. 27A, a first annular winding unit 33a is prepared by winding two conductor wires 32 each composed of a continuous copper wire having a circular cross section coated with an electrical insulator for a predetermined number of winds, and a second annular winding unit 33b is prepared by continuing to wind the two conductor wires 32 for a predetermined number of winds. Next, as shown in FIG. 27B, first and second intermediate star-shaped winding units 34A and 34B composed of two conductor wires are prepared by forming each of the first and second annular winding units 33a and 33b into a star shape in which adjacent pairs of slot-housed portions 34a are alternately joined on an inner circumferential side and an outer circumferential side by coil end portions 34b. Next, the first and second intermediate star-shaped winding units 34A and 34B are folded over at a linking portion of the conductor wires 32 where the first and second intermediate star-shaped winding units 34A and 34B are linked, and as shown in FIG. 27C, a star-shaped winding unit 35 is prepared by stacking the first and second intermediate star-shaped winding units 34A and 34B on top of one another such that the slot-housed portions 34a are superposed and the coil end portions 34b face each other in a radial direction.
A first star-shaped winding unit 35 prepared in this manner is mounted to the stator core 15 such that each of the slot-housed portions 34a is housed in Slot Numbers 1, 7, etc., through 67 of the slots 15a and such that the winding ends thereof extend outward from Slot Numbers 1 and 7 of the slots 15a, becoming the a-phase winding phase portion 30a. A second star-shaped winding unit 35 is mounted to the stator core 15 such that each of the slot-housed portions 34a is housed in Slot Numbers 2, 8, etc., through 68 of the slots 15a and such that the winding ends thereof extend outward from Slot Numbers 38 and 44 of the slots 15a, becoming the d-phase winding phase portion 30d. A third star-shaped winding unit 35 is mounted to the stator core 15 such that each of the slot-housed portions 34a is housed in Slot Numbers 3, 9, etc., through 69 of the slots 15a and such that the winding ends thereof extend outward from Slot Numbers 15 and 21 of the slots 15a, becoming the c-phase winding phase portion 30c. A fourth star-shaped winding unit 35 is mounted to the stator core 15 such that each of the slot-housed portions 34a is housed in Slot Numbers 4, 10, etc., through 70 of the slots 15a and such that the winding ends thereof extend outward from Slot Numbers 28 and 34 of the slots 15a, becoming the f-phase winding phase portion 30f. A fifth star-shaped winding unit 35 is mounted to the stator core 15 such that each of the slot-housed portions 34a is housed in Slot Numbers 5, 11, etc., through 71 of the slots 15a and such that the winding ends thereof extend outward from Slot Numbers 5 and 11 of the slots 15a, becoming the b-phase winding phase portion 30b. And a sixth star-shaped winding unit 35 is mounted to the stator core 15 such that each of the slot-housed portions 34a is housed in Slot Numbers 6, 12, etc., through 72 of the slots 15a and such that the winding ends thereof extend outward from Slot Numbers 24 and 30 of the slots 15a, becoming the e-phase winding phase portion 30e. 
As shown in FIG. 28, the winding end of the a-phase winding phase portion 30a extending outward from Slot Number 7 of the slots 15a, the winding end of the b-phase winding phase portion 30b extending outward from Slot Number 11 of the slots 15a, and the winding end of the c-phase winding phase portion 30c extending outward from Slot Number 15 of the slots 15a are led around an upper portion of the coil end portions 34b (axially outside the stator core 15), gathered together, and integrated by a crimp 31. Here, the electrically-insulating coating on the winding end of each of the conductor wires 32 is removed and the winding ends of the conductor wires 32 are electrically connected by solder to constitute a neutral point N. Hence, the first three-phase alternating-current winding 160A is obtained, in which the a-phase winding phase portion 30a, the b-phase winding phase portion 30b, and the c-phase winding phase portion 30c are formed into a Y connection.
The winding end of the d-phase winding phase portion 30d extending outward from Slot Number 38 of the slots 15a, the winding end of the e-phase winding phase portion 30e extending outward from Slot Number 30 of the slots 15a, and the winding end of the f-phase winding phase portion 30f extending outward from Slot Number 34 of the slots 15a are led around an upper portion of the coil end portions 34b, gathered together, and integrated by a crimp 31. Here, the electrically-insulating coating on the winding end of each of the conductor wires 32 is removed and the winding ends of the conductor wires 32 are electrically connected by solder to constitute a neutral point N. Hence, the second three-phase alternating-current winding 160B is obtained, in which the d-phase winding phase portion 30d, the e-phase winding phase portion 30e, and the f-phase winding phase portion 30f are formed into a Y connection.
Here, the remaining winding ends of the a-phase winding phase portion 30a, the b-phase winding phase portion 30b, and the c-phase winding phase portion 30c constitute output wires Oa, Ob, and Oc, respectively, and the remaining winding ends of the d-phase winding phase portion 30d, the e-phase winding phase portion 30e, and the f-phase winding phase portion 30f constitute output wires Od, Oe, and Of, respectively. The output wires Oa, Ob, and Oc are connected to the first rectifier 12A and the output wires Od, Oe, and Of are connected to the second rectifier 12B to constitute the circuit shown in FIG. 26.
Moreover, because two conductor wires 32 are installed together, the a-phase winding phase portion 30a is constructed such that windings having the same number of turns are connected in parallel. The a-phase winding phase portion 30a is installed such that bundles of the conductor wires 32 extending outward from any given slot 15a are distributed half each to first and second circumferential sides. The rest of the winding phase portions 30b, 30c, 30d, 30e, and 30f are constructed in a similar manner.
The a-phase, b-phase, and c-phase winding phase portions 30a, 30b, and 30c are each given a phase difference corresponding to an electrical angle of 120 degrees, and the d-phase, e-phase, and f-phase winding phase portions 30d, 30e, and 30f are each given a phase difference corresponding to an electrical angle of 120 degrees. In addition, the d-phase, e-phase, and f-phase winding phase portions 30d, 30e, and 30f are given a phase difference corresponding to an electrical angle of 30 degrees relative to the a-phase, b-phase, and c-phase winding phase portions 30a, 30b, and 30c, respectively.
In the first conventional stator 8 constructed in this manner, the first stator winding 16 is constituted by the first and second three-phase alternating-current windings 160A and 160B, output from the first and second three-phase alternating current-windings 160A and 160B being rectified by the first and second rectifiers 12A and 12B. Thus, twelve diodes 12a are required to constitute the first and second rectifiers 12A and 12B, giving rise to cost increases. Because the first and second rectifiers 12A and 12B are positioned in ventilation channels for cooling airflows generated by the fans 5, ventilation resistance increases and the flow rates of the cooling airflows decrease, causing cooling of the first stator winding 16 to deteriorate. In addition, because the diodes 12a, which are heat-generating parts, are positioned at upstream ends of the ventilation channels for the cooling airflows, if the number of diodes 12a is increased, the cooling airflows supplied to cool the first stator winding 16 positioned downstream in the ventilation channels for the cooling airflows are heated, also causing cooling of the first stator winding 16 to deteriorate.
In order to solve problems of this kind, as shown in FIG. 29, it has been proposed that output from a second conventional stator winding 16A is rectified by a single rectifier 12C, the second conventional stator winding 16A being constructed such that an axe2x80x2-phase winding phase portion 30axe2x80x2, a bxe2x80x2-phase winding phase portion 30bxe2x80x2, and a cxe2x80x2-phase winding phase portion 30cxe2x80x2 are prepared by connecting together in series those winding phase portions among the a-phase, b-phase, c-phase, d-phase, e-phase, and f-phase winding phase portions 30a, 30b, 30c, 30d, 30e, and 30f having a phase difference corresponding to an electrical angle of 30 degrees, and forming the axe2x80x2-phase winding phase portion 30axe2x80x2, the bxe2x80x2-phase winding phase portion 30bxe2x80x2, and the cxe2x80x2-phase winding phase portion 30cxe2x80x2 into a Y connection to constitute a single three-phase alternating-current winding 160C.
A second stator 8A in which the second stator winding 16A is installed will now be explained with reference to FIGS. 30 and 31.
In the second stator 8A, the a-phase, b-phase, c-phase, d-phase, e-phase, and f-phase winding phase portions 30a, 30b, 30c, 30d, 30e, and 30f constituting the second stator winding 16A are constructed such that each of the slot-housed portions 34a of the star-shaped winding units 35 are housed in every sixth slot 15a in a similar manner to the first stator 8 described above.
The winding end of the a-phase winding phase portion 30a extending outward from Slot Number 7 of the slots 15a and the winding end of the d-phase winding phase portion 30d extending outward from Slot Number 38 of the slots 15a are led around an upper portion of the coil end portions 34b (axially outside the stator core 15), gathered together, and integrated by a crimp 31. Here, the electrically-insulating coating on the winding end of each of the conductor wires 32 is removed and the winding ends of the conductor wires 32 are electrically connected by solder. Hence, the axe2x80x2-phase winding phase portion 30axe2x80x2 is constructed, in which the a-phase winding phase portion 30a and the d-phase winding phase portion 30d, which have a phase difference corresponding to an electrical angle of 30 degrees, are connected in series.
The winding end of the b-phase winding phase portion 30b extending outward from Slot Number 11 of the slots 15a and the winding end of the e-phase winding phase portion 30e extending outward from Slot Number 30 of the slots 15a are led around an upper portion of the coil end portions 34b (axially outside the stator core 15), gathered together, integrated by a crimp 31, and electrically connected by solder. Hence, the bxe2x80x2-phase winding phase portion 30bxe2x80x2 is constructed, in which the b-phase winding phase portion 30b and the e-phase winding phase portion 30e, which have a phase difference corresponding to an electrical angle of 30 degrees, are connected in series.
The winding end of the c-phase winding phase portion 30c extending outward from Slot Number 15 of the slots 15a and the winding end of the f-phase winding phase portion 30f extending outward from Slot Number 34 of the slots 15a are led around an upper portion of the coil end portions 34b (axially outside the stator core 15), gathered together, integrated by a crimp 31, and electrically connected by solder. Hence, the cxe2x80x2-phase winding phase portion 30cxe2x80x2 is constructed, in which the c-phase winding phase portion 30c and the f-phase winding phase portion 30f, which have a phase difference corresponding to an electrical angle of 30 degrees, are connected in series.
Next, the winding end of the d-phase winding phase portion 30d extending outward from Slot Number 44 of the slots 15a, the winding end of the e-phase winding phase portion 30e extending outward from Slot Number 24 of the slots 15a, and the winding end of the f-phase winding phase portion 30f extending outward from Slot Number 28 of the slots 15a are led around an upper portion of the coil end portions 34b, gathered together, integrated by a crimp 31, and electrically connected by solder. Hence, the single three-phase alternating-current winding 160C (the second stator winding 16A) is obtained, in which the axe2x80x2-phase winding phase portion 30axe2x80x2, the bxe2x80x2-phase winding phase portion 30bxe2x80x2, and the cxe2x80x2-phase winding phase portion 30cxe2x80x2 are formed into a Y connection.
In the second stator 8A constructed in this manner, as shown in FIG. 31, a first interphase crossover portion 36a-d which is constituted by the winding ends of the a-phase winding phase portion 30a and the d-phase winding phase portion 30d, a second interphase crossover portion 36b-e which is constituted by the winding ends of the b-phase winding phase portion 30b and the e-phase winding phase portion 30e, and a third interphase crossover portion 36c-f which is constituted by the winding ends of the c-phase winding phase portion 30c and the f-phase winding phase portion 30f are arranged so as to overlap in a radial direction of the stator core 15. A neutral-point connection portion 37 constituted by the winding ends of the d-phase winding phase portion 30d, the e-phase winding phase portion 30e and the f-phase winding phase portion 30f also overlaps the interphase crossover portions 36a-d, 36b-e, and 36c-f in a radial direction. The remaining winding ends of the a-phase winding phase portion 30a, the b-phase winding phase portion 30b, and the c-phase winding phase portion 30c constitute output wires Oaxe2x80x2, Obxe2x80x2, and Ocxe2x80x2 of the axe2x80x2-phase winding phase portion 30axe2x80x2, the bxe2x80x2-phase winding phase portion 30bxe2x80x2, and the cxe2x80x2-phase winding phase portion 30cxe2x80x2, respectively, and the joint portion of the neutral-point connection portion 37 constitutes a neutral point N. The output wires Oaxe2x80x2, Obxe2x80x2, and Ocxe2x80x2 are connected to the single rectifier 12C, constituting the circuit shown in FIG. 29.
In the first stator 8 used in the conventional automotive alternator, as described above, the first stator winding 16 is constituted by the first and second three-phase alternating-current windings 160A and 160B, output from the first and second three-phase alternating current-windings 160A and 160B being rectified by the first and second rectifiers 12A and 12B. Thus, one problem has been that the number of diodes 12a constituting the first and second rectifiers 12A and 12B is increased, giving rise to cost increases. Because ventilation resistance in the ventilation channels for the cooling airflows generated by the fans 5 increases, reducing the flow rates of the cooling airflows, and the cooling airflows supplied to cool the first stator winding 16 are heated by the heat from the diodes 12, another problem has been that cooling of the first stator winding 16 deteriorates.
In the second stator 8A used in the conventional automotive alternator, the problems with the first stator 8 described above are solved by constituting the second stator winding 16A by the single three-phase alternating-current winding 160C. However, because the interphase crossover portions 36a-d, 36b-e, and 36c-f are arranged so as to overlap in a radial direction of the stator core 15, the following new problems have arisen.
The crossover portions on the radial outside among the interphase crossover portions 36a-d, 36b-e, and 36c-f are less likely to be exposed to the cooling airflows and the stator winding 16A is not cooled efficiently, preventing the suppression of temperature increases in the second stator 8A. As a result, declines occur in the output of the second stator 8A. This problem is further exacerbated because the neutral-point connection portion 37 overlaps the interphase crossover portions 36a-d, 36b-e, and 36c-f in a radial direction.
Now, it is also conceivable that the interphase crossover portions 36a-d, 36b-e, and 36c-f could be exposed to the cooling airflows by varying the axial heights of the interphase crossover portions 36a-d, 36b-e, and 36c-f. In that case, because the axial heights of the interphase crossover portions 36a-d, 36b-e, and 36c-f are higher, ventilation resistance increases, and wind noise also increases.
Because the crimps 31 (joint portions) of the interphase crossover portions 36a-d, 36b-e, and 36c-f are in close proximity and short-circuiting between the crimps 31 occurs easily as a result of vibration, etc., electrical insulation deteriorates. This problem is further exacerbated because the joint portion of the neutral-point connection portion 37 is in close proximity to the joint portions of the interphase crossover portions 36a-d, 36b-e, and 36c-f.
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator enabling cooling and electrical insulation to be improved and wind noise to be reduced by making interphase connections between winding phase portions having a phase difference corresponding to an electrical angle of 30 degrees among six winding phase portions installed in a stator core in which slots are formed at a ratio of two per phase per pole so that output from a stator winding can be rectified by a single rectifier, and disposing the interphase crossover portions connecting the winding phase portions having a phase difference corresponding to an electrical angle of 30 degrees so as to be offset in a circumferential direction from each other.
To attain the above object, according to one aspect of the present invention, there is provided an automotive alternator including a stator having, an annular stator core in which slots are disposed at a ratio of two per phase per pole, and a stator winding mounted to the stator core. The stator winding is provided with six winding phase portions each installed in a slot group including every sixth slot of the slots such that each of the slot groups is successively offset by one slot. Each pair of the six winding phase portions having a phase difference corresponding to an electrical angle of approximately 30 degrees is connected by an interphase crossover portion. The interphase crossover portions are arranged so as to be separated in an axial direction from coil ends of the stator winding and so as to be offset in a circumferential direction so as not to overlap each other in a radial direction.
Therefore, there is provided an automotive alternator in which cooling and electrical insulation of the stator is improved and wind noise is reduced.
The stator winding may be constructed into a single three-phase alternating-current winding by forming three connected winding portions into a Y connection, each of the connected winding portions being formed by connecting a pair of the winding phase portions having a phase difference corresponding to an electrical angle of approximately 30 degrees by means of the interphase crossover portions. The stator winding may be constituted by first and second three-phase alternating-current windings in each of which three of the winding phase portions having a phase difference corresponding to an electrical angle of 120 degrees are formed into a Y connection, the first and second three-phase alternating-current windings being constructed in parallel by connecting pairs of the winding phase portions having a phase difference corresponding to an electrical angle of approximately 30 degrees by means of the interphase crossover portions. The stator winding may be constructed into a single three-phase alternating-current winding by forming three connected winding portions into a delta connection, each of the connected winding portions being formed by connecting a pair of the winding phase portions having a phase difference corresponding to an electrical angle of approximately 30 degrees by means of the interphase crossover portions. The interphase crossover portions may be constituted by continuous conductor wires coated with an electrical insulator. The interphase crossover portions may be constituted by conductor wires drawn in an axial direction from the winding phase portions and a connection member connecting the conductor wires at a position separated in an axial direction from the coil ends. The automotive alternator may include a rectifier for converting alternating current from the stator into direct current, the connection member being formed integrally in the rectifier so as not to overlap with a diode constituting the rectifier relative to a radial direction. The interphase crossover portions may have a joint portion formed by joining together end portions of conductor wires drawn from the winding phase portions, the joint portion being positioned in a ventilation channel for a cooling airflow above the coil ends. End portions of the conductor wires may be formed with a rectangular cross section, the end portions of the conductor wires being joined by bringing side surfaces constituted by long sides of the rectangular cross sections into close contact with each other. A neutral point constituting the three-phase alternating-current windings may be constituted by a joint portion formed by joining together end portions of conductor wires drawn from the winding phase portions, the joint portion being positioned in a ventilation channel for a cooling airflow above the coil ends. The joint portion may be formed by TIG welding. The interphase crossover portions may be disposed so as to be dispersed generally uniformly in a circumferential direction. Coil ends of the stator may be constructed in an aligned state in which coil end portions of the winding phase portions are arranged uniformly in a circumferential direction. The winding phase portions may be constructed by linking together a large number of short conductor segments. The winding phase portions may be constituted by a plurality of wave windings in each of which one continuous conductor wire is installed so as to alternately occupy an inner layer and an outer layer in every sixth slot of the slots. The winding phase portions may be constituted by conductor wires having a circular cross section. The winding phase portions may be connected in parallel by connecting radially-adjacent pairs of conductor wires at winding ends.